1. Field of the Invention
The present invention relates to an apparatus and method for supporting heterogeneous systems in a multi-hop relay broadband wireless communication system. More particularly, the present invention relates to an apparatus and method for performing communication according to a frame structure capable of simultaneously supporting heterogeneous systems in a multi-hop relay broadband wireless communication system.
2. Description of the Related Art
A next generation communication system (i.e., a 4th Generation (4G) communication system) aims to provide various Qualities of Service (QoS) with a data rate of about 100 Mbps. In particular, the 4G communication system has evolved to ensure mobility and QoS in a Broadband Wireless Access (BWA) communication system (e.g., a Local Area Network (LAN) system, a Metropolitan Area Network (MAN) system, etc.). A representative example of the communication system includes an Institute of Electrical and Electronics Engineers (IEEE) 802.16d communication system and an IEEE 802.16e communication system.
The IEEE 802.16d communication system and the IEEE 802.16e communication system use an Orthogonal Frequency Division Multiplexing (OFDM)/Orthogonal Frequency Division Multiple Access (OFDMA) scheme for a physical channel.
In a conventional IEEE 802.16e communication system, signaling communication is performed between a fixed Base Station (BS) and a Mobile Station (MS) through a direct link. Therefore, a wireless communication link may be established with high reliability between the BS and the MS. However, since the BS has a fixed location in the IEEE 802.16e communication system, a wireless network structure has low flexibility. Accordingly, it is difficult to provide an effective communication service in a wireless environment where traffic distribution and call demands rapidly change.
To address such a disadvantage, a data delivery method using a multi-hop relay scheme may be used in a conventional cellular wireless communication system (e.g., the IEEE 802.16e communication system) by the use of a fixed Relay Station (RS), a mobile RS, or an MS. The multi-hop relay wireless communication system may reconfigure a network by rapidly handling changes of a communication environment, and may further effectively manage an overall wireless network. For example, the multi-hop relay wireless communication system may extend cell coverage area and increase system capacity. That is, when a channel condition is poor between a BS and an MS, an RS may be installed between the BS and the MS to configure a multi-hop relay path via the RS. Therefore, a wireless channel having an improved channel condition may be provided to the MS. In addition, the multi-hop relay scheme may be used in a cell boundary area where a channel condition from the BS is poor, and thus a high-speed data channel may be provided and the cell coverage area may be extended.
In the multi-hop relay wireless communication system, a BS may use a relay service of an RS to provide a communication service to an MS located outside the coverage area of the BS. In order to provide the relay service, a specific time at which data is transmitted by the BS, the RS, and the MS needs to be indicated by defining a physical frame structure.
A DownLink (DL) frame and an UpLink (UL) frame of the BS are divided into an access zone and a relay zone. In an access zone of the DL frame, the BS or the RS transmits data to the MS, and in a relay zone of the DL frame, the BS transmits DL data, which is used to provide a relay service to the MS, to the RS. In addition, in an access zone of the UL frame, the MS transmits data to the BS or the RS, and in a relay zone of the UL frame, the RS transmits UL data, which is used to provide a relay service to the MS, to the BS.
As described above, multi-hop relay communication may be achieved by using the RS. However, the multi-hop relay communication scheme may be used only when the BS, the RS, and the MS correspond to the same system. If at least one of the BS, the RS, and the MS corresponds to two or more wireless systems, the multi-hop relay communication scheme may not be used.
Wireless communication systems evolve to provide a high-speed data service in comparison with a legacy system or to address an implementation issue. In such a system evolution process, various systems may coexist in the same area according to a degree of compatibility with the legacy system. For example, a new system evolved from the legacy system may be installed in an area where an IEEE 802.16e system (i.e., legacy system) is installed. In this case, the new system must be able to provide services not only to a legacy MS but also to a new MS. In other words, when an MS corresponding to the legacy system coexists with an MS corresponding to the new system, there is a need for a frame structure capable of providing services to the two MSs.